Process for spinning composite acrylic fibers

ABSTRACT

ACRYLIC COMPOSITE FIBERS HAVING LATENT COILY CRIMPS, USEFUL IN THE MANUFACTURE OF BULKY YARN PRODUCTS HAVING A HIGH DEGREE OF FLEXIBILITY, ARE PREPARED BY SPINNING TWO DIFFERENT ACRYLONITRILE POLYMERS TO OBTAIN AN ACRYLIC COMPOSITE FIBER, STRETCHING THE FIBER, SUBJECTING THE FIBER TO STRUCTURE COLLAPSING TREATMENT, HEAT-TREATING THE FIBER IN A RELAXED STATE, AND RESTRETCHING THE FIBER.

United States Patent C M 3,562,378 PROCESS FOR SPINNING COMPQSITE ACRYLIC FIBERS Yoshimasa Fajita, Kazumi Nakagawa, Keitaro Shimoda, and Koji Miyashita, Saidaiji, Japan, assignors to Japan Exlan Co., Ltd.

No Drawing. Continuation-in-part of application Ser. No. 687,934, Sept. 6, 1967, which is a division of application Ser. No. 402,932, Oct. 9, 1964. This application Aug. 20, 1968, Ser. No. 753,859 Claims priority, application Japan, Oct. 14, 1963,

38/ 55,198 Int. Cl. Dld 5/22 US. Cl. 264-168 2 Claims ABSTRACT OF THE DISCLOSURE Acrylic composite fibers having latent coily crimps, useful in the manufacture of bulky yarn products having a high degree of flexibility, are prepared by spinning two different acrylonitrile polymers to obtain an acrylic composite fiber, stretching the fiber, subjecting the fiber to structure collapsing treatment, heat-treating the fiber in a relaxed state, and restretching the fiber.

This application is a continuation-in-part application of our application Ser. No. 687,934, filed Sept. 6, 1967, and now abandoned, which in turn is a divisional application of our application Ser. No. 402,932 filed Oct. 9, 1964, now abandoned.

The present invention relates to a method of producing composite fibers composed predominantly of acrylonitrile polymer, and having highly satisfactory shrinking properties.

A composite fiber composed of two or more polymers which have different thermal behaviors, said polymers being eccentrically disposed about the fiber axis and throughout the fiber length, would develop three-dimensional coil crimps upon heating, due to their differential thermal shrinkage. The textile products spun, knitted or woven by using such a fiber would have not only a satisfactory bulk but also a hand and elasticity that is commonly associated with woolen products. However, when a composite fiber having already had its potential coil crimps developed during its manufacture is employed in the textile process, its three-dimensional crimps would cause the fiber to creep around the card cylinder, with the result that not only is the spinning operation made difficult, but also part of the crimp will be lost during the spinning, knitting or weaving process, and/ or finishing operation so that satisfactory bulkiness is not obtained in the final products.

Therefore, there have been proposed several methods of controlling the development of crimps during the composite fiber-making process and, only after a composite fiber is spun, heating the same to develop the desired coil crimps. For example, US. Pat. No. 2,439,815 discloses a process for manufacturing composite fibers with latent self-crimping properties which comprises simultaneously spinning two dissimilar thermoplastic materials with different thermal shrinking properties into a composite filament, drafting the .same, and non-plasticizing (eg. drying) the resulting fiber under tension.

It has been found, however, that when composite fibers are composed of acrylic polymers, no fibers having a practical utility and satisfactory yarn quality can be manufactured simply by following the sequence of spinning, drawing, and drying under tension. Furthermore, it has been found that the shrinkability or shrinking power of the fiber in the formation of coil crimps due to the differential thermal shrinkage of dissimilar fiber com- 3,562,378 Patented Feb. 9, 1971 ponents is extremely small and, while coil crimps may be fully developed if such a composite fiber is heated in a fully relaxed state in which the fiber has complete freedom of motion, this ideal state cannot be attained when a product containing such a fiber is treated on a large or commercial scale where the fiber would be subject to various restrictive forces such as the load under its own weight, the restrictions derived from the construction of the knit or weave itself, the tension due to the flow of the treating fluids used in dyeing and finishing, etc. These forces restrict the freedom of movement of the fiber, thereby inhibiting the formation of etficient coil crimps and, accordingly, the production of satisfactory bulky products.

Therefore it is a primary object of this invention to provide acrylic composite or conjugated fibers having potential or latent coil crimps and also having a high shrinkability (or shrinking power) so as to overcome the above mentioned drawbacks associated with conventional acrylic composite fibers.

Another object of this invention is to provide a method of producing acrylic composite or conjugated fibers having potential or latent crimps and high shrinkability or shrinking power.

Other objects of this invention will be apparent from the following detailed explanation.

Briefly, the fiber of the present invention is composed of two or more different acrylonitrile polymers having different thermal shrinkage and arranged in lamination along the entire length of the fiber and eccentrically in respect to the fiber axis, and is characterized in that it possesses potential coil crimps which can be developed upon heating and exhibits a rate of shrinkage of from 5% to about 16.0 and a shrinkability of at least 30 mg./ d. when immersed in hot water at 98 C.

These composite fibers may be manufactured, according to this invention, by extruding two or more dissimilar spinning solutions of different acrylic polymers (different in thermal shrinkage) simultaneously through a nozzle by awet spinning method, stretching the resulting composite filaments in a conventional manner, subjecting the filaments to structure collapsing treatment, heat treating the same in a relaxed state, and further stretching the filaments 1.05 to 1.25 times their initial length at temperatures from 100 C. to 260 C.

It is appropriate that some of the terms used in this specification and the claims appended hereto be defined before the present invention is described in further detail. The term shrinkability or shrinking power refers to the tension which will be induced in a shrinkable fiber when the fiber, while it is being held stationary at both ends, is immersed in hot water, as measured with a strain measuring device. More particularly the sample is pre pared by aligning side by side about 100 monofilaments and securing at both ends a portion 30 cm. in length. The length of the sample is determined so as to have an initial tension of 10 mg./d., and the tension that works on the fiber when the latter is immersed in hot water at 98 C. is plotted against time. The tension would reach its peak in l-2 seconds, and then, would fall off as the stress is relieved. This maximum tension is defined as the shrinkability or shrinking power of the particular fiber in hot water.

The rate of shrinkage is the degree of shrinkage of the fiber when it is treated with hot water at 98 C. for 10 minutes in a relaxed state. The length of the fiber is measured under a tension of 10 mg./d.

The composite fiber of the present invention consists of two polymers which, respectively, are composed predominantly of acrylonitrile, i.e. those which comprise at least 50% by weight of acrylonitrile and which differ from each other in thermal shrinkage.

Thus when one polymer is polyacrylonitrile, the other may be a copolymer of acrylonitrile and at least one ethylenically unsaturated monomer copolymerizable there with. Of course, both of the polymers may be copolymers having different thermal shrinkage. The ethylenically unsaturated copolymerizable monomers are well known in the art and include, for example, lower alkyl acrylates and methacrylates, acrylamide and methacrylamide, acrylic acid and methacrylic acid, vinyl acetate, vinyl chloride, vinyl pyridines, methallyl sulfonic acid and its salts.

In any case, however, these acrylonitrile polymers should be used in such a combination that the resulting filaments would have a rate of shrinkage of from 5% to about 16.0% upon being immersed in hot Water at 98 C.

The composite or conjugated fibers may be formed in a well known and conventional manner. Thus, the different spinning solutions of difierent polymers are simultaneously extruded into a coagulating bath through a common spinning nozzle so that each filament would be composed of different polymer sections eccentrically arranged along the full length of the filament with respect to the filament axis. The method and apparatus for producing such composite, laminated or conjugated fibers are well known in the art and do not constitute a feature of this invention.

The solvents for the spinning solutions and composi tion of the coagulating bath may also be conventional ones well known in the art of wet-spinning of fibers of acrylonitrile polymers.

The important feature of the present invention is in the particular combination and sequence of treatments after spinning, that is, spinningstretching for orientationstructure collapsing (non-structurization) treatmentheat treatment in a relaxed statefurther stretching (X105- 1.25) a 100-260 C.

Thus, after spinning, the composite filaments are subjected to an initial stretching. The purpose of this stretching is for orientation of the fiber structure. Generally, the filaments are stretched 5 to 15 times the initial length at a temperature of 80 to 150 C. in hot air, steam, or a liquid medium such as hot water.

The stretched or oriented fibers are then subjected to a structure collapsing treatment (sometimes referred to as non-structurization). This treatment is very important for improving the crimp characteristics of the composite fibers and hence the bulkiness of the final products. The structure collapsing treatment is conducted by drying the fibers in a drying atmosphere under particular correlated conditions of temperature and humidity until substantially all of the water has been evolved from the fibers so that the structure is collapsed. The dry-bulb temperature should be within the range of ZOO-260 F., and the minimum and maximum percentages of relative humidity should be those corresponding to wet-bulb temperatures of 122 F. and 176 F. respectively. Best results are achieved when the dry-bulb temperature is within the range of ZOO-260 F. and the minimum and maximum percentages of relative humidity are those corresponding to wet-bulb temperatures of 158 F. and 167 F. A more detailed discussion of the particular correlated conditions of temperature and humidity is described in US. Pat. No. 2,984,912.

After the drying or structure collapsing treatment, the fibers are subjected to a relaxation treatment. This relaxation is also important in the present invention for improving the fiber properties, particularly for increasing the knot strength and preventing fibrillation of the fibers. The relaxation is conducted by treating the fibers at a temperature of from 100 to 160 C. in a relaxed state, preferably in boiling water or in steam under pressure.

Then, the fibers are stretched 1.05 to 1.25 times the initial length at a temperature of 100-260 C. in hot air, hot aqueous medium or steam.

Through these particular treatments in the above-mentioned order, a high-shrinking composite fiber can be man- 4 ufactured which has a rate of shrinkage ranging from 5% to about 16.0 and a shrinkability of at least 30 mg./d. in hot water at 98 C.

In order that a composite fiber may shrink by overcoming various restrictive forces and develop its potential coil crimps completely after it is made into spun yarn or textile or knit products, it has been found that the composite fiber must have a shrinkability of at least 30 mg./d. In addition, in order to produce a sufiicient bulk in the fiber, it must have a rate of shrinkage ranging from 5% to about 16.0% when immersed in hot Water at 98 C. for 10 minutes.

Where a conventional acrylic fiber composed of a single polymeric substance is to be used as a high-shrinking fiber, it has generally been acknowledged that such a fiber must have a rate of thermal shrinkage of from 15 to 30%, or possibly more, in order to attain sufficient bulk. In contrast, in the case of the composite fiber of the present invention which would give rise to threedimensional coil crimps, a highly satisfactory bulk may be obtained by giving it a rate of thermal shrinkage of from 5% to about 16.0%. If the fiber were given a rate of shrinkage above about 16.0%, as for example 16.2%, the excess shrinkage would result in an unduly great yarn density, which would detract from the bulk and, accordingly, the hand of the final product. Thus, the rate of shrinkage is preferably not over about 16.0%. Composite fibers possessing such a comparatively low rate of shrinkage and, yet, a high shrinkability of at least 30 mg./d. can only be manufactured according to the method of the present invention.

By using the composite fiber of the present invention alone, bulky yarn products having a high degree of flexibility may be manufactured. In addition, it is also pos sible to manufacture mix-spun bulky yarns by spinning the present composite fiber with natural fibers, such as Wool and cotton, or various non-shrinking or less-shrinking man-made fibers in a well known and conventional manner. Furthermore, the composite fiber of this invention may also be mix-spun with a composite fiber which has not been re-stretched after the relaxation treatment.

EXAMPLE 1 A copolymer of acrylonitrile and 10% methyl acrylate and a copolymer of 88% acrylonitrile and 12% methyl acrylate were separately dissolved in a 50% aqueous solution of sodium thiocyanate to prepare two spinning solutions. Equal amounts of said solutions were simultaneously extruded through a spinning nozzle into an 8% aqueous solution of sodium thiocyanate. The resulting tow was washed with water and then stretched 8 times its initial length in boiling water. The spinning noz- Zle used had 500 orifices (each 0.08 mm. in diameter). The tow was then dried in a highly humid atmosphere at a dry-bulb temperature of C. and a wet-bulb temperature of 70 C. until the filaments had a moisture content of less than 3%. The filaments were then treated in a relaxed state in boiling water for 10 minutes. Then the filaments were mechanically crimped, treated with finishing oil, and dried to prepare a composite filament A of 6 d. The same tows after the said relaxation were guided over two hot plates at C. and stretched 1.07, 1.15 and 1.22 times the initial length, respectively. The stretched filaments were mechanically crimped to prepare shrinking composite fibers B, C and D, respectively. Using the staples of A, B, C, and D, four different spun yarns (each 4/22) were manufactured, and the hanks of these yarns were then dried by means of a hank dyer. The dyeing conditions were as follows.

Dye

TABLE 1 Shrinking charaeter- Properties of isties of filaments spun yarns Shrink- Rate of ability, shrinkage, BulkimgJd. percent ness Hand A 7 1 x x B 31 5.1 o C 84 10.8 o 0 D 160 16.2 A A N0'1E.Ii1 the above table, 0 denotes good A fair and x poor.

The yarn manufactured from low-shrinking composite fiber A had a poor bulk owing to the insufiicient development of coil crimps due to the restrainiig motion of the liquid in the dye bath. On the other hand, the yarn manufactured from high-shrinking composite fiber D which has a rate of shrinkage of 16.2%, showed an excessive shrinkage so that the yarn was too great in fiber density and, therefore, too tight or compact. What are needed for satisfactory yarns are degrees of shrinkability that would overcome the restraining flow of the dye solution in the dyeing equipment, and also appropriate rates of shrinkage that would not allow the yarn to be compacted too tightly. Stated dilferently, the composite fiber must have a shrinkability of at least 30 mg./d. and a rate of shrinkage of from to about 16.0%.

EXAMPLE 2 The staples of low-shrinking composite fiber A and high shrinking composite fibers B, C, and D, all of which were prepared in the same manner as Example 1, were mixspun in various proportions into yarns (each 422). The hanks of these yarns were respectively dyed by means of a hank dyeing machine under the same conditions as described in Example 1.

The shrinkability values and properties of the spun yarns are summarized in Table 2.

NorE.-In the above table, 0 denotes good, A fair and x poor.

If the yarn is poor in shrinkability, it will have an insufficient bulk. On the other hand, if too much of a fiber having an excessively great rate of shrinkage is employed, the resultant yarn tends to be compacted too tightly to yield a kind hand when treated in the relaxed state. Thus, yarns having satisfactory bulk and hand can be obtained only when they have a shrinkability range of to 100 1ng./d.

6 EXAMPLE 3 A copolymer of 90% acrylonitrile, 9.5% methyl acrylate, and 0.5% sodium methallyl sulfonate, and a copolymer of 88% acrylonitrile, 11.5 %methyl acrylate and 0.5% sodium methallyl sulfonate were separately dissolved in a aqueous solution of sodium thiocyanate to prepare two different spinning solutions. These spinning solutions were simultaneously extruded through a spinning nozzle into an 8% aqueous solution of sodium thiocyanate to form composite filaments. The spinning nozzle had 500 orifices or holes, each being 0.08 mm. in diameter. The tow of the composite filaments was washed with water and stretched 8 times the initial length in boiling Water. The same tow was divided into three groups, which were subjected to different treatments respectively. Thus one was subjected to structure collapsing treatment by drying the same in an atmosphere at a dry-bulb temperature of 110 C. and a wet-bulb temperature of C. until the water content in the filaments was reduced to less than 3% (this filament is referred to as E). The second one was dried to a water content of less than 3% in a hot air medium at C. having a relative humidity of 4% (this filament is referred to as F). The third one was not subjected to any thermal drying (this filament is referred to as G). These filaments or fibers were treated in saturated water vapor at 100 C. for 10 minutes in a relaxed state. The relaxed filaments were then mechanically crimped, treated with a finishing agent and dried to obtain three different composite fibers of 3 (1. These three kinds of tow were stretched 1.20 times the initial length while passing between a pair of hot plates heated at C. The filaments were again mechanically crimped to obtain three different shrinking composite fibers E, F and G. These filaments were cut into staples (114 mm.) and r spun into yarns (2/36) respectively, which were hank dyed in the same manner and under the same conditions as in Example 1. The bulky appearance of these dyed yarns as well as the crimp characteristics of the fibers as immersed in boiling water for 10 minutes in a relaxed state are shown in Table 3.

It will be apparent from the above results that the structure collapsing treatment is very important in this invention in the development of excellent crimps in the fibers and bulkiness in the final products.

What we claim is:

1. A method of manufacturing a composite acrylic fiber which comprises extruding at least two spinning solutions of acrylonitrile polymers having different thermal shrinkages each containing at least 50% by weight of acrylonitrile, any remainder of the polymers being at least one ethylenically unsaturated monomer copolymerizable with the acrylonitrile, simultaneously through a spinning nozzle into a coagulating bath to form a composite filament, initially stretching the filament 5 to 15 times its length, subjecting the filament to structure collapsing at a dry-bulb temperature of 200260 F. and a wet-bulb temperature of 122176 F., heat-treating the filament in a relaxed state at a temperature of 100160 C., and stretching the filament 1.05 to 1.25 times its initial length at a temperature of 100-260 C.

2. A method as in claim 1 wherein the initial stretch is conducted at 80-150 C.

(References on following page) References Cited 3,111,366 11/1963 Fujita et a1 264-182UX UNITED STATES PATENTS 3,397,426 8/1968 Fujita 61', a1. 264210FX 0 11/1962 Bradley 3,404,204 10/1968 Nakagawa et a1. 264168X 5/1965 Luiita et a1. 264168X FOREIGN PATENTS 8/1968 Olson 264-168X 5 633,098 5/1963 Belgium 264-Bicomp. Fiber 2/ 1969 Holfeld 2872 3/1969 Luiita et a1. 264--168X JAY H. WOO, Primary Examiner 4/1969 Ryan 264-168X 4/ 1968 Sisson 264Bic0mp. Fiber US. Cl. X.R. 12/1964 Humphrey et a1 28-72A 10 2 -1 2, 

